Nonlinear effects in biodynamics

Abstract

Biological systems are often characterized by large deformations, nonlinear constitutive equations and complex arrangements of soft tissues, bone, and fluids. Linear analysis usually provides at least a rough description which is sufficient for many purposes, but nonlinear theory is often required for accurate description. Wave propagation in blood flow is definitely a nonlinear phenomenon but may be linearized for many applications. In the arteries, the nonlinearity is less significant than in veins which distort severely. The “pistol shot” effect requires nonlinearity. In shock and vibration of the entire body or large parts of it, nonlinear wave propagation and vibration are significant. In recent work on seat ejection problems, the spine is represented by nonlinear beam theory. In head injury due to impact, most theoretical treatments to date use linearized elastic and acoustic theory. At fracture and physiologic damage levels, nonlinear properties and dynamics are important but not yet analyzed extensively.